Iron(II) dichloride complexes bearing a tridentate nitrogen donor ligand were investigated for the homopolymerization of tert-butyl acrylate after activation with methylaluminoxane. Two new complexes were synthesized, 2,6-bis[1-(cyclohex-ylimido)ethyl]pyridine iron chloride (FeCl2) and 2,6-bis[1-(isopropylimido)ethyl]pyridine FeCl2, and the single-crystal X-ray structure of the latter one was determined. Turnover frequencies of the catalysts during polymerization ranged from 36 to 241 cycles/mol/h. The obtained polymers exhibited weight-average molecular weights ranging from 24,000 to 438,500 g/mol, and the molar mass distribution varied between 1.8 and 4.3. Activity of the catalytic system and the molar mass of the polymer are influenced by the ligand structure of the complexes as well as other polymerization conditions such as monomer concentration and temperature. (C) 2003 Wiley Periodicals, Inc.